If the linking document is being served over HTTP, then those URLs will point to http://adactio.com/journal/tags/nerdiness and https://huffduffer.com/js/global.js but if the linking document is being served over HTTP Secure, the URLs resolve to https://adactio.com/journal/tags/nerdiness and https://huffduffer.com/js/global.js.

Writing the src attribute relative to the linking document’s protocol is something that Remy is already doing with his HTML5 shim:

If you have a site that is served over both HTTP and HTTPS, and you’re linking to a CDN-hosted JavaScript library—something I highly recommend—then you should probably get in the habit of writing protocol-relative URLs: